USB problem/Thunderbolt on Mac mini M4

I have a Mac Mini M4 Pro and have seen the following. I have an external NVMe enclosure on the Thunderbolt port in the back. That drive stays connected!

I have another external enclosure with old HDD drives for my Time Machine backup connected on the back port via a USB-C to USB-B cable. That enclosure does NOT stay connected and I get a message every morning that my Time Machine was not ejected correctly.

I have moved it to the front port and so far it has been staying connected, but I will monitor for a few more days.

In summary I am experiencing USB 3.x devices on the back ports loosing connection. TB devices on the back ports remaining connected.

Update 2 - after replacing both cables with short, direct connectors….. I thought I nailed it but I was wrong. The SSD TimeMachine drive still threw Illegal Dismount Errors. The USB drive with a hard disk however, didn't. I think it has to do with the SSD drive getting it's power through the USB-C Port. I have moved the SSD connection to the front of the Mini M4 and haven't seen a Dismount Error since. I ordered 2 right angle connectors so I can route the cable along the side of the Mini, otherwise it looks dorky to have a cable poking out the front.

You're welcome.

To put it simply, the Thunderbolt ports on the Mac are a combination of high-speed data connection and power delivery, and it also carries compatibility with USB protocols. You can therefore use it to connect simple, less expensive USB devices to your Mac and the more expensive Thunderbolt specified storage, monitors, hubs and other devices. Killing two birds with one stone, as it were. That's why in descriptions, the ports are often labeled as Thunderbolt/USB. I agree that marketing could be better.

I agree no modifications should be necessary, a USB C connection alone should be secure, but I am finding the same thing, very lose, and any touch causes a connection break.

should I return it?

Looks like your mind’s already made up, so much for “30 years of troubleshooting” 😂

Anyways, vent here Feedback - Mac mini - Apple, might help. All the best!

The rear-panel USB-C ports on the M4 Mac mini are multi-purpose ports that support

• Traditional USB (I'm guessing at up to 10 Gb/s)
• USB4 (up to 40 Gb/s)
• DisplayPort
• Thunderbolt 4 (up to 40 Gb/s)
• [M4 Pro chip models only] Thunderbolt 5 (up to 120 Gb/s)

They adapt to whatever is plugged into them.

The front-panel USB-C ports on the M4 Mac mini are single-purpose ports that support

• Traditional USB (up to 10 Gb/s)

You can think of the USB-C connector as being like the concept of a "Swiss Army knife", and the things that live on it as being like the "blades". Some Swiss Army knives have more blades than others; and some USB-C ports offer support for more types of things than others.

I had the same problem on new mac mini m4 : 1 apple keyboard and 1 optical mouse, both wired and fitted with a simple usb to usb-c adaptor, and connected to any of the front usb-c or rear thunderbolt slots had them disconnected after a while. Using a non-powered usb hub didn't change this.

After lots of tryouts the following works (but don't ask me why) : optical mouse connected to front usb-c slot and apple keybord connected to a non-powered hub connected to rear thunderbolt port. Doesn't work without the hub !

See hardware usb values included

Sounds like the problem is how well USB-C sockets hold plugged-in cables, in general – rather than anything to do with Thunderbolt. I believe in this regards, the Lightning connector was a bit better than USB-C – even though the Lightning connector is not nearly as capable as USB-C.

After much trial and error, the USBC issue is definitely on the rear ports and happens during sleep. I've had constant disconnects of hard drives connected directly (I've tried 3 different drives), usb hubs (I've tried 3, the last one is powered). Plugged in the front, I've not had any problems. It manifests itself when the Mac mini goes into sleep mode. I get the message that my Time Machine drive was ejected incorrectly. Hopefully this is a software bug; not good!

Had two USB drives plugged into rear USB-C ports, one an SSD with a short cable (USB-C to USB-C) used as Time Machine BU, the second was a USB-A through a USB-A to USB-C pigtail with an extended, longer USB cable to the 2nd disk drive. The OS was flagging dismounts with the TimeMachine drive. When I moved the 2nd cable to the front USB-C, the dismounts with the still rear attached TimeMachine SSD went away. IMHO the rear connectors are underpowered to be fully utilized.

PanamaMacUser wrote:

I'm new to Mac. Recently bought a Mac Mini with M4 chip. My problem is with the front ports (not the rear ports). I have an XCellon USBC-4311-2 hub and a wireless Logitech mouse. The mouse stopped working. Switched the hub to one of the back ports and the mouse worked again. After rebooting, the the front ports started working again. Took the computer to a local authorized dealer. They ran some checks and they say all is fine. Today it happened again.

Xcellon – USBC-4311-2 4-Port Slim USB 3.1 Gen 1 Type-C Hub

That's a hub with four USB-A (USB 3.0) ports that attaches to a computer via an uplink cable that has a USB-C connector on the end.

It does not appear to have any provision for operating off its own power supply, which could be a problem. If it is simply distributing USB 3.0 bus power (900mA @ 5V = 4.5W), there might not be enough to go around once you started plugging drives into it. I've seen portable drives that wanted to take 896 mA just for a single drive. If it is hoping to negotiate for higher amounts of power from the host, using USB-C Power Delivery, the description and specifications make no mention of it.

But that shouldn't matter if you are just attaching a keyboard and a mouse – and since the only ports on the thing are USB ones, it shouldn't need a DisplayPort Alt Mode, Thunderbolt, or USB4 signal that is only available on the rear-panel ports of the M4 Mac mini. It should work with any of the Mac Mini's five USB-C ports - front or back.

Update - Replaced the long USB extender cable with adapters with a single "high speed" USB-C to Micro-B Cable (no adapters) and have been using the rear ports without "disconnect" error for a few days.

I think it is a physical hardware problem in my case— the rear ports do not provide a secure fit. Slight movement of a cable is enough to disconnect an external drive. In my case, I have a powered OWC 11-Port Thunderbolt Dock (with 2 drives attached) connected to a rear port. I've now tried 2 thunderbolt cables to connect the dock to the rear ports on the M4 Mac Mini and I've tried 2 of the 3 ports.* Both cables and both ports have disconnected with a slight movement of the cables (at the Mac Mini end of the cable). Both cables are new that came with products (i.e. external drive enclosures).

The last thing I'm going to check is to see if the insecure fit problem also exists with an Apple-branded Thunderbolt cable (iow, if the Mac Mini M4 doesn't play nice with non-Apple cables). I have a nearby Apple store, so probably will just take it in to have them see for themselves.

I'd suggest giving your cable the jiggle test to see if the physical port is the problem.

(*I haven't messed with the 3rd rear port because my Home directory is running on an external drive there; it also disconnected once, causing problems, and I'm leaving it untouched with my fingers crossed).

drew_como wrote:

With this thread gaining traction over the last few weeks, I really hope that someone from Apple takes notice.

Apple doesn't normally participate in these forums, except to moderate them. You might want to try to raise the issue through Apple Support or through Apple's Feedback page.

I would suggest including as much specific, helpful information as you can, about

• Which combinations of devices and ports don't work
• Which do

Although most people reporting problems in this thread are having problems with one set of ports (front or back), the people who are having problems with the front ports may be having a different problem (as far as root causes are concerned) than the people who are having problems with the back ports.